what are the codes auto or manual price sounds high to me but without knowing whats wrong its impossible to say if thats totally unreasonable a couple of years ago i put a rebuilt tranny and new torque converter into an old explorer i had and that was if youre going to a dealer they may be insisting on new parts and it could very well be the cost of the new parts that is the difference either way get an estimate from another mechanic and then youll know if the first one is throwing rediculous numbers at you trying to make a quick buck as someone else pointed out the car is only worth about the cost of this repair and with mileage as high as yours is id probably cut my losses and get another car